In this work, the reproductive biology of Etmopterus spinax (Chondrichthyes: Etmopteridae) is analyzed. A total of 475 specimens (275 females and 200 males) were collected at depth of 390-1573 m in 2008-2012 in Sardinian waters. The species is sexually dimorphic with females growing to a larger size than males and attaining greater size at first maturity (at around 83% of the maximum observed size in both sexes). The immature, mature, resting females and mature males were recorded in all seasons while expecting and expectant females were caught in spring and winter respectively. The presence of active males only in winter suggested that the mating could occur at this time. It has an alternate reproductive cycle with the ovarian and uterine phases occurring separately. It has a low fecundity, with a mean ovarian fecundity of 17 oocytes. The estimated coefficients indicate that this species has a vulnerable life cycle, typical of deep-water squalid sharks

In this work, the reproductive biology of Etmopterus spinax (Chondrichthyes: Etmopteridae) is analyzed. A total of 475 specimens (275 females and 200 males) were collected at depth of 390-1573 m in 2008-2012 in Sardinian waters. The species is sexually dimorphic with females growing to a larger size than males and attaining greater size at first maturity (at around 83% of the maximum observed size in both sexes). The immature, mature, resting females and mature males were recorded in all seasons while expecting and expectant females were caught in spring and winter respectively. The presence of active males only in winter suggested that the mating could occur at this time. It has an alternate reproductive cycle with the ovarian and uterine phases occurring separately. It has a low fecundity, with a mean ovarian fecundity of 17 oocytes. The estimated coefficients indicate that this species has a vulnerable life cycle, typical of deep-water squalid sharks